Here's a dropdown list I'm sure you're all familiar with:
Notice how there's no Mx option in there. Well, sometimes, it's possible to add your own title in here and actually be successful with the form submission. I'm going to explain how to do it, but first, the caveats:
This isn't always going to work and you may experience issues further down the line if it does.
If it does work:
All of the above has happened to me in the past, and it's by far not a comprehensive list, so please remember that your mileage may vary
So, without further ado, let's learn how this works.
<select>
<option value="">Select a title</option>
<option value="Mr">Mr</option>
<option value="Ms">Ms</option>
<option value="Miss">Miss</option>
<option value="Mrs">Mrs</option>
<option value="Dr">Dr</option>
</select>
value='Mr'
means that "Mr" is what's sent to the website if this is selected. This is what you will need to change in order to send "Mx" or another title. Change this by double clicking it to enable text entry and then type in, making sure all the speech marks and/or quotes are the same as they originally were.
<option value="Mx">Mr</option>
>Mr<option>
means that "Mr" is what appears in the dropdown list visually and is nothing to do with what is sent with the rest of the form. You can change this as well if you want to, as it lets you see which option you've actually changed.
<option value="Mx">Mx</option>
And that's it. Try it out on the dropdown list at the top of this page. There's no page to submit to, but you can try out messing with the code.
Some websites do weird things with their dropdown boxes with span tags or div tags, etc. If it's not a simple form, use the search function in the DOM Inspector to find one of the titles (I recommend "Mrs" as that string of letters in that order doesn't come up very often in typical web pages) and then replace every one you find in the code. Sometimes that works, sometimes not.
I will link to this page elsewhere on this website when I come across sites where the form can be modified in this way and if it's successful, along with any warnings. However, you can attempt to use this anywhere and see what happens. Please let me know if you're successful with any site using this method and I'll add it here and credit you (if you wish). Please email please@dontgender.me
Good luck